What is a key feature of the lung mechanics in mammals?

A key feature of lung mechanics in mammals is that the lungs remain in contact with the thoracic wall. This close association allows for efficient ventilation and ensures that as the thoracic cavity expands and contracts during breathing, the lungs also expand and contract accordingly. This relationship is crucial for proper air movement into and out of the lungs, as it helps maintain the necessary intrapleural pressure that facilitates the mechanics of inhalation and exhalation.

In mammals, the lungs are surrounded by pleural membranes, which create a pleural cavity filled with pleural fluid. This arrangement generates negative pressure that helps keep the lungs inflated and enables the lungs to follow the movements of the thoracic wall during the breathing process. This is essential for effective gas exchange to occur in the alveoli, which are the small air sacs in the lungs where oxygen and carbon dioxide are exchanged.

The other choices involve inaccuracies regarding lung mechanics. For example, gas exchange does not occur in the trachea; it primarily takes place in the alveoli. Furthermore, lung inflation is not directly reliant on positive air pressure but rather occurs through negative pressure generated by the diaphragm and intercostal muscles. Lastly, while the heart rate can influence breathing, breathing itself is primarily driven by the mechanics